If patients are suffering from problems with the heart rhythm or are considered to be at high risk of serious heart rhythm problems it is sometimes useful to study the electrical behaviour of the heart in more detail that that afforded by the ordinary ECG. EPS is performed in the cardiac catheter laboratory and electrodes are passes on long catheters through the veins in the groin into the heart. These wires are then used to study how the electricity travels in the heart in its normal rhythm, and during a palpitation where possible known as ‘mapping’. It may be necessary to use electrical stimulation to elicit an abnormal rhythm as part of the procedure. EPS can be performed as a diagnostic procedure or sometimes combined with treatment, by performing an ablation.

All test results should be treated with caution and interpreted in the context of a clinical assessment.